1. Field of the Invention
The invention relates to a twin-wire former for producing a fibrous web, in particular a paper, board or tissue web, from a fibrous suspension. The twin-wire former includes two endless wire belts arranged to form a twin-wire zone, in which, in a first section of the twin-wire zone, the two wire belts run over a dewatering element in the form of a rotating forming roll and together form a wedge-like inlet gap which picks up the fibrous stock suspension directly from a headbox fitted at an angle relative to an imaginary first horizontal plane, and in which, in a second section of the twin-wire zone, the two wire belts with the fibrous web forming between them run downward over further dewatering elements at an angle (α) of 10° to 60° relative to an imaginary first vertical plane. At the end of the second section of the twin-wire zone, the two wire belts run over a first deflection device with a lower vertex and then over at least one separating device which acts over the machine width and, in the area in which one of the wire belts is led away from the forming fibrous web and the other wire belt. A second deflection device with an upper vertex is arranged after the separating device to deflect the wire belt that carries the forming fibrous web.
2. Discussion of Background Information
A twin-wire former of this type is known from the German Published Specification DE 198 03 591 A1 (PB 10656 DE) from the Applicant. The twin-wire former has two wire belts (lower wire and upper wire), which together form a twin-wire zone. In a first part of the twin-wire zone, in which the two wire belts run over a dewatering element in the form of a rotating forming roll, the two wire belts together form, directly at the forming roll, a wedge-like inlet gap, which picks up the fibrous stock suspension directly from a headbox (“gap former”). In a second section of the twin-wire zone, the two wire belts with the fibrous web forming between them run steeply downward over further dewatering elements, for example over a plurality of forming foils and/or at least one forming shoe, preferably at an angle of 10° to 60° relative to an imaginary vertical plane. At the end of the second section of the twin-wire zone, the wire belts run over a deflection device and then over a separating device, which separates one of the wire belts from the forming fibrous web and from the other wire belt.
The disadvantage with this known twin-wire former is that, because of the relatively great forming roll diameter, which can assume a value for example between 1.5 and 2.5 m, it has a very large overall height. This large overall height leads to problems with regard to the height of the hall or crane, particularly in the case of rebuilds, and therefore to increased rebuilding costs and overhaul or operating costs.